There is no single predetermined dosage for CBD products. Every human body is different and what suits you might not suit the other person. So, when you buy CBD oil in USA, it is always recommended to purchase from a well-known and reputed brand and start with a smaller serving size until you find what works for you. Also, consider consulting a health expert or medical professional to determine if CBD is right for you, especially if you are on medications to ensure CBD and your medications do not conflict.